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collapse after NBCD turn-off in JT-60U fully non-inductive reversed shear dischargesTakei, Nahoko; Nakamura, Yukiharu; Ushigome, Masahiro*; Suzuki, Takahiro; Aiba, Nobuyuki; Takechi, Manabu; Tobita, Kenji; Takase, Yuichi*; Fukuyama, Atsushi*; Jardin, S. C.*
Plasma Physics and Controlled Fusion, 49(3), p.335 - 345, 2007/03
Times Cited Count：7 Percentile：25.44(Physics, Fluids & Plasmas)Non-disruptive -collapses with a regular intermittency have been observed after a forced turn-off of neutral beam current drive (NBCD) in JT-60U fully non-inductive, reversed shear (RS) discharges. Self-consistent transport simulations with improved core confinement and linear MHD stability analysis have first clarified that redistribution of return current induced after the NBCD turn-off lowers the safety factor of magnetic shear reversal, leading to the n =1 kink-ballooning instability with localized modes around internal transport barrier (ITB). It was also pointed out that an increase of the bootstrap current under continuous NB heating can lead to ITB reconstruction and thus causes subsequent beta-collapses.
Nakamura, Yukiharu; Tobita, Kenji; Fukuyama, Atsushi*; Takei, Nahoko; Takase, Yuichi*; Ozeki, Takahisa; Jardin, S. C.*
Nuclear Fusion, 46(8), p.S645 - S651, 2006/08
Times Cited Count：3 Percentile：10.55(Physics, Fluids & Plasmas)A self-consistent simulation, including a model for improved core energy confinement, demonstrates that externally applied, inductive current perturbations can be used to control both the location and strength of internal transport barriers (ITBs) in a fully non-inductive tokamak discharge. We find that ITB structures formed with broad non-inductive current sources such as LHCD are more readily controlled than those formed by localized sources such as ECCD. Through this external control of the magnetic shear profile, we can maintain the ITB strength which is otherwise prone to deteriorate when the bootstrap current increases.
Takei, Nahoko; Ushigome, Masahiro*; Suzuki, Takahiro; Nakamura, Yukiharu; Takase, Yuichi*
Europhysics Conference Abstracts (CD-ROM), 30I, 4 Pages, 2006/00
no abstracts in English
Takei, Nahoko; Nakamura, Yukiharu; Tsutsui, Hiroaki*; Yoshino, Ryuji; Kawano, Yasunori; Ozeki, Takahisa; Tobita, Kenji; Iio, Shunji*; Shimada, Ryuichi*; Jardin, S. C.*
Plasma Physics and Controlled Fusion, 46(12), p.1815 - 1830, 2004/12
Times Cited Count：3 Percentile：9.92(Physics, Fluids & Plasmas)no abstracts in English
reversed shear plasmasTakei, Nahoko; Nakamura, Yukiharu; Kawano, Yasunori; Tsutsui, Hiroaki*; Ozeki, Takahisa; Tobita, Kenji; Sugihara, Masayoshi; Iio, Shunji*; Shimada, Ryuichi*; Jardin, S. C.*
Europhysics Conference Abstracts, 28G, 4 Pages, 2004/00
no abstracts in English
Takei, Nahoko; Nakamura, Yukiharu; Kawano, Yasunori; Tsutsui, Hiroaki*; Ozeki, Takahisa; Tobita, Kenji; Sugihara, Masayoshi; Iio, Shunji*; Shimada, Ryuichi*; Jardin, S. C.*
Journal of Plasma and Fusion Research SERIES, Vol.6, p.554 - 557, 2004/00
no abstracts in English
Nakamura, Yukiharu; Tsutsui, Hiroaki*; Takei, Nahoko*; Shirai, Hiroshi; Sugihara, Masayoshi; Gribov, Y.*; Ozeki, Takahisa; Tobita, Kenji; Iio, Shunji*; Jardin, S. C.*
Journal of Plasma and Fusion Research SERIES, Vol.6, p.196 - 198, 2004/00
no abstracts in English
Nakamura, Yukiharu; Tsutsui, Hiroaki*; Takei, Nahoko*; Sakamoto, Yoshiteru; Fujita, Takaaki; Sugihara, Masayoshi; Ozeki, Takahisa; Tobita, Kenji; Konishi, Satoshi; Iio, Shunji*; et al.
Europhysics Conference Abstracts, 27A, 4 Pages, 2003/00
no abstracts in English
Takei, Nahoko; Ozeki, Takahisa; Smolyakov, A. I.*; Isayama, Akihiko; Hayashi, Nobuhiko; Iio, Shunji*; Shimada, Ryuichi*
Journal of Plasma and Fusion Research SERIES, Vol.5, p.386 - 389, 2002/00
no abstracts in English
Saigusa, Mikio*; Kikuchi, Yusuke*; Takei, Nahoko*; Kanazawa, Sadayoshi*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi
Fusion Engineering and Design, 53(1-4), p.505 - 510, 2001/01
Times Cited Count：11 Percentile：61.58(Nuclear Science & Technology)no abstracts in English
Saigusa, Mikio*; Takei, Nahoko*; Kanazawa, Sadayoshi*; Kikuchi, Yusuke*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi
Journal of Plasma and Fusion Research SERIES, Vol.3, p.383 - 386, 2000/00
no abstracts in English
Takei, Nahoko; Ushigome, Masahiro*; Suzuki, Takahiro; Takechi, Manabu; Aiba, Nobuyuki; Nakamura, Yukiharu; Takase, Yuichi*
no journal, ,
no abstracts in English
Nakamura, Yukiharu; Tobita, Kenji; Fukuyama, Atsushi*; Takei, Nahoko; Takase, Yuichi*; Ozeki, Takahisa; Jardin, S. C.*
no journal, ,
no abstracts in English
Nakamura, Yukiharu; Tobita, Kenji; Takei, Nahoko; Takase, Yuichi*; Fukuyama, Atsushi*; Nishio, Satoshi; Sato, Masayasu; Jardin, S. C.*
no journal, ,
no abstracts in English
Nakamura, Yukiharu; Takei, Nahoko; Tobita, Kenji; Sakamoto, Yoshiteru; Fujita, Takaaki; Fukuyama, Atsushi*; Jardin, S. C.*
no journal, ,
From the aspect of fusion burn control in steady state DEMO plant, the significant challenges are to maintain its high power burning state of 
3 - 5 GW without burning instability, and also to keep its desired burning profile relevant with internal transport barrier (ITB) that generates high bootstrap current. A self-consistent simulation has pointed out that in the high power fusion DEMO plant there is a close, nonlinear interplay between the fusion burnup and the current source of non-inductive, ITB-generated bootstrap current. Consequently, as much distinct from usual burning conditions with lower power (
1GW), the self-ignited fusion burn at a high power burning state of 3 - 5 GW becomes so strongly self-organized that any of external means except fuelling can not provide the effective control of the stable fusion burn. The paper presents a simulation modeling of the burning stability coupled with the self-ignited fusion burn and the structure-formation of the ITB.
